Synchronizing mechanism



Nov. 1941. D. A. DICKEY 2,261,145

SYNCHRONIZING MECHANISM- Filed Oct. 8, 193'? 4 Sheets-Sheet l DAM/EA. A. 0K: KEV

Nov. 4, 1941.

D. A. DICKEY SYNCHRONIZING MECHANISM 4 Sheets-Shet 2 Fild Oct. 8, 1937 47' A A/EV:

Nov. 4, 1941. D. A. DICKEY SYNCHRONIZING MECHANISM 4 Sheets-Sheet 4 Filed Oct. 193'? Vl/EN7'OR 0,4/v/ EL 4. D/cKEV Patented Nov. 4, 1941 2,261,145 synonnomzmo MECHANISM Daniel A. Dickey, Dayton, Ohio Application October 8, 1937, Serial No. 168,025

Claims.

(Granted under the act of March 3, 1883, as amended April 30, 1928; 370 0. G- 757) The invention described herein may be manufactured and used by or for the Government for governmental purposes, without the payment to me of any royalty thereon.

It is an object of my invention to synchronize a plurality of prime movers which during normal operation may vary in revolutions per unit of time from one another or from a master speed of rotation device.

More specifically, my invention relates to apparatus for synchronizing a plurality of such prime movers as those encountered in multiengined aircraft power plants in order to reduce to a minimum structural vibrations and auditory fatigue caused by the operation 01' the engines of such power plants out of synchronism.

It is well known to those skilled in the art that aircraft employing multi-engined power plants having more than one propeller, are subiect to a very disagreeable beat or drumming noise whenever one or more engines rise above or fall below the operating revolutions of the power plant as a Whole. The aforesaid phenomena subjects the personnel operating the air craft to severe auditory fatigue and may set up destructive vibrations in the aircraft structure itself.

In aircraft employing only two propellers, it is a comparatively simple matter to eliminate beat phenomena due to engine revolution inequalities by merely varying the speed of revolution of one of the aforesaid engines until the beat disappears. However, when three or more propellers are employed, it will be readily seen that elimination of the beat phenomena becomes a highly complicated matter because of the fact that it is extremely diiilcult for operating personnel of the aircraft to tell which propellers are causing the beat. Previously, therefore, this difilculty has proven a serious drawback to the extended use of airplanes having three or more independently driven propellers, particularly for use in carrying passengers. The safety feature introduced by the greater number of independently driven propellers, however, is extremely desirable.

It is of course possible to set engine revolutions approximately th same by using the tachometers attached to each engine, but it is impossible with tachometers alone to set engine revolutions close enough to a master revolution indicator to eliminate the objectionable beat referred to above for the reason that mechanical tachometers only read within fifteen and electric tachometers only read within fifty revolutions of the true turning rate of the motor to which they are applied, while as little as a five revolutions difl'erenc in the turning rate of multi-engined power plants will produce the beat phenomena.

It is a still further object of my invention to automatically synchronize the engine revolutions of multi-engined aircraft power plants.

I further propose to automatically adjust the springs of th governors oi' automatic propeller pitch control systems so as to give each governor spring the exact adjustment necessary to make the governor correct theengine speed exactly to that maintained by the master speed of rotation device.

Other objects and advantages of my invention will become apparent from the following description taken in connection with the accompanying drawings, it being clearly understood that the same are by way of illustration and example only and are not to be taken as in. any way limiting the spirit or scope ofmy invention. The spirit and scope of my invention is to be limited only by the prior art, and by the terms of the appended claims.

Referring to the drawings, in which numerals of like character designate similar parts throughout the several views:

Fig. 1 shows diagrammatically th electric equipment required to drive the alternators operating the synchronizer units controlling pitch change;

Fig. 2 is a partial cross-sectional view of one form of synchronizer unit adapted for application to electrically operated propeller pitch changing mechanisms:

Fig. 3 is a fractional cross-sectional view of another form of synchronizer unit adapted for application to hydraulically operated propeller pitch changing mechanisms;

Fig. 4 shows application of the synchronizer device of Fig. 2 to an electrically operated variable pitch propeller; and

Fig. 5 shows application of the synchronizer devicepf Fig. 3 to a hydraulically operated variable pitch propeller.

Fig. 1 shows, in diagrammatical form, the exact electrical equipment required when a direct current source is available to drive the alternators operating electric synchronizer units controlling propeller pitch change of a multi-engined power plant. With deletion of certain parts hereinafter specifically referred to, the same general system may be applied to hydraulic synchronizer units controlling propeller pitch change of multi-engined power plants. Direct current (from a source not shown) is led into a switch panel I, provided with a tachometer 2 and later referred to parts. An alternator 3, positively coupled to a direct current motor 4, is connected to the tachometer 2 by means of a flexible drive shaft 5. The motor 4 is connected to the aforesaid direct current source by means of double pole switches 6 and l, a rheostat control 8 and wires 9, l0, and II; the latter two wires also having common connection with the alternator 3 of the motor-generator set (3-4). Upon closing of the switches 6 and I, the alternator 3 is brought to any desired speed through employment of the control 8 in conjunction with the tachometer 2. The three lead wires of the alternator 3 are connected to the inner three of five main wires l2, l3, l4, l5, and I6, which find common connection to each of the two (or more) synchronizer units ila, i'lb, etc. of Figs. 1, 2 and 4, or to the synchronizer units lfla, etc. of Figs. 3 and 5.

In order that the balance of the diagrammatic representations of Fig. 1 may be more readily understood, the physical parts disposition of the all electric synchronizer units Fla and ill) of Fig. 1 are next described according to the showing of Fig. 2. In this particular form of synchronizer unit, a split housing of the unit no is composed of a housing portion i9 encasing an alternating current motor 20, a housing portion 2| encasing a differential assembly 22, a ball bearing 23 supporting the right extremity of a counter shaft 24, and a housing portion 25 encasing the remaining synchronizer parts. The differential assembly 22 is composed of a combination spider-clutch 26, two differential gears 21, a gear 28 forming one side of the assembly 22 and fixed to the drive shaft of the motor 20 by means of a pin 29, and a gear 30 forming the other or opposite side of the assembly 22 and journalled to a threaded spindle 3| by means of ball bearings 32 and having its right extremity fixed to the slip-disc portion of the spider-clutch 25. It will be noted that a drive shaft 33 is parallelly spaced from the spindle 3! at the extreme left of the housing portion 25 by means of ball bearings 34 and a spacer collar 35. A flexible shaft 36 is secured to the drive shaft 33 by means of a retaining collar 31 and square tipped driving end 38. The inner end of the drive shaft 33 flares out into a disc-like member 39. 40 is fixed to the left face of the member 39 by means of rivets 41. The right-hand face of the member 39 is provided with a pair of projections 42 which carry two combined weights and L- shaped supporting arms 43 by means of bearing pins 43a.

As thus far described, rapid turning of the member 39, by the flexible shaft 35 will cause the combined weight and L-shaped supporting arms 43 to tend to rotate 90 degrees outwardly. To prevent such rotation, the housing portion 25 is provided with a counter weighing or variable loading mechanism 44 composed of a fixed base member 45. with inner bearing lined central tube 46, a compression spring 41, and a displaceable or slidable base 48 longitudinally adjusted upon the outer surface of central tube by means of the threaded spindle 3i. The top end of the compression spring 41 is seated upon a flared out portion 49 of a spindle 50 passing through and guided by the inner bearing portion of the central tube 46. The spindle 50 further including a short journal 5| projecting to the left of the flared out portion 49, and a running bearing 52 mounted on the journal 5|. The right-hand ex- A gear tremity of the spindle 50 passes through insulating sheets 53a and 53b, backing the base member 45, to seat upon an inwardly pressing bearing block 54 of a U-shaped spring 55, in such a manner that two adjoining contact points 55a and 55b provided upon the free end of the spring 55 are floatingly retained in axial alignment with two oppositely spaced contact points 51 and 53. Mid-spacing of contact points 55a and 55b obtains only when the centrifugal force generated by the rotating weight portions of the arms 43 exactly equals the longitudinal force generated by a predetermined setting of the compression spring 41. If the centrifugal force dominates, the cylindrically cammed surfaces of the inturned portions of the combined weights and L-shaped supporting arms 43 displace the running bearing housing I58 to the right of the parts showing of Fig. 2, thereby closing contact points 56b58. On the other hand, if the longitudinal force of the spring 41 dominates, the running bearing housing I58 is displaced to the left of the parts showing of Fig. 2, thereby closing contact points 580-51. It is readily obvious to those skilled in the art that continuing left-hand movement of the slidable base 48 (from the low revolution per minute setting of Fig. 2) will require like continuing increase in the rotation speed of the rotating weight portions of the arms 43, if the contact points 560 and 55b are to remain mid-way between the contact points 51 and 58. A brief description of the wiring interconnecting the propeller pitch changing motors 59a and 59b of Figs. 1 and 4 to their power source will complete parts enumeration essential to an understanding of non-synchronous operation of the propeller shown in Fig. 4. Having thus clearly set forth non-synchronous operation of a portion of the structures of Figs. 1, 2 and 4 (which may be stated as old in the art), synchronous operation of the remaining structures of the aforesaid figures (and unknown to the present art) is more readily described and understood.

Let it be assumed that the pilot of a multiengined aircraft has accomplished normal throttle lever advance for a given flight maneuver and upon reference to his engine tachometers, finds that one engine is turning less than a desired number of revolutions per minute. Disregarding for the moment my ultimate problem of bringing a. lagging engine into "true" synchronism with one or more engines already turning at a desired number of revolutions per minute, which problem, it has already been stated, can not be successfully solved by mere tachometer corrected" throttle readjustment, let it be further assumed that aircraft engine 50a of Figs. 1 and 4 is the lagging engine in question. In the past, the pilot merely brought the throws of switches 5i and 62 into right-hand engagement with terminals C and E of the panel I and closed the double pole switch 6. Current from a source of power, not shown, thereupon flowed from terminal Al--2 and E of panel I directly to terminals A and E of the propeller pitch changing motor 59a, causing decreased pitch rotation of blades 53m and 53b of propeller 64 shown in Fig. 4. The engine a thereupon immediately increased in number of revolutions per minute. Upon attainment of desired engine speed, the pilot simply opened the double pole switch 8. For lagging of engine 501), the throws oi switches 65 and 66 are brought into right-hand engagement with terminals G and I of the panel I. For over-speeding of engine 50a, switch Si is thrown to the right and switch 82 is thrown to the, left; while over-speeding of engine 88b is corrected by throwing switch 68 to the right and switch 88 to the left. Interconnection between pairs of terminals E-E, D-D', B-B', K-K', I-I', H-H', FF', and J-J provided by means of wires 81 through 18, respectively, while terminal AI-2 is connected to main wire I2 by means of wire 15.

In the above method 01' electrically increasing' or decreasing engine revolutions without change in engine throttle setting, no invention is involved in the provision of terminals 13 and F of the panel I. In the past, closing of the double pole switch 6 and simultaneous throwing of both switches 85 and 8| to-the left, made possible current flow from terminals B and F of the panel I directly to terminals B and F of the U-shaped springs 55a and 55b, respectively. But a glance at the wiring diagrams of the latter springs and their interconnection to the propeller pitch changing motors 59a and 58b, shown in Fig. 1, immediately suggests two additional methods which are obviously available for increasing or decreasing engine revolutions while maintaining fixed throttle setting. Through innumerable stages of left hand advancement of the base 48 from the positioning shown in Fig. 2, either by manual rotation of a flexible shaft extension fixed to the outer extremity of the threaded spindle 3Ia or by means of direct interconnection between the threaded spindle 3Ia and the alternating current motor 28a, the counterweighing mechanism a can be varyingly weighed to produce an innumerable series of predetermined engine speeds. From our previous knowledge of the lateral movements of the spindle 50a, it therefore follows that with any one advancement of the slidable base 48a, lagging of the engine 68a causes closingof contact points 5611-51, while over-speeding thereof causes closing of contact points 56b-58. Further reference to the wiring diagram of Fig. 1 indicates that if the double pole switches 6 and 1 of panel I are closed during the aforesaid closing of contact points, terminals B or F are automatically interconnected with terminals E or I (causing decreased pitch rotation of propeller blades 63a and 53b of Fig. 4) upon engine lag, while ter minals B and F are automatically interconnected with terminals D or H (causing increased pitch rotation) upon over-speeding of the engines 68a or 68b.

Having clearly set forth that which is old in the art, I now propose to disclose improvements in synchronizers never heretofore existing. Referring to Fig. 2, I have previously stated that the gear 48 is fixed to the back face of the disclike member 39. A mating gear 16, fixed to the left extremity of the counter shaft 24 by means of a pin 11, is provided with a dog tooth slot 18. The aforesaid end is journalled to the housing portion 25 by means of the ball bearing 23, a collar 19, and a pin 88. The right-hand extremity of the shaft 24 is further provided with a conventional disc clutch 8|. Interposed between the gear 16 and the clutch 8|, and substantially encasing the shaft 24, is provided a clutch engaging mechanism 82. The clutch 8i consists of a driven face 83, backed by a collar 84 fixed to the shaft 24 by means of a pin 85; a driving face 86 provided with a dog tooth'slot 81; and a disengaging spring 88, encased within spring recesses 89 and 98 provided in the aforesaid clutch faces. The engaging mechanism 82 consists of a hollow ironspindle 8|, with centrally disposed and outwardly turned magnet flange 82, and an electric magnet 83. It will be noted that the outer extremities of the spindle 8| are provided with dog teeth 84 remaining at all times in positive sliding engagement with slots 18 and 81 of the gear 18 and the clutch driving face 88. The magnet 83 is composed of a c-shaped magnet 85, fixed to the housing portion 25 by means of screws 88 and lock washers 81; an energizing coil 88, fixed to the right extremity of the magnet by means of screws 88 and lock washers I88; and wires 18-18 and 18 connected respectively with terminal MI and I82. In the showing of Fig. 1, closing of the throws of switch I83 or switch I84 automatically causes engagement of the clutch Me or 8H) through energization of the clutch engaging mechanism 82a or 82b. The effect of the aforesaid clutch engagement will be set forth in the paragraph immediately following.

The outermost periphery of driven clutch face 83 is provided with a gear portion I85-designed to be held in constant engagement with a gear portion I86 provided upon the left-hand extremity of the gear 38 of the differential assembly" 22. The spring 88 of the disc clutch 8| normally holds the driving and driven faces 86 and 83 of the aforesaid clutch apart in such a manner that the gears 38I86 and I85 are free to spin without developing enough torque to make the spider-clutch 28 of the differential assembly 22 turn, even though the gear 28 fixed to the drive shaft of the alternating current motor 28 continues to turn. Referring to Fig. 1, the clutches 8Ia and Bio are engaged magnetically by means of an energizing coil 82a and an energizing coil 82b fixed to the energizer units Ila and III). The clutch engaging mechanism 82a is electrically interconnected to the single pole switch I83 of panel I by means of wire 18, while the clutch engaging mechanism 82b is similarly connected to the single pole switch I84 by means of wire 18. As long as the clutch 8i of Fig. 2 remains engaged, the combined gears 38--I86 will freely rotate about their ball bearing 32 attachment to the threaded spindle 3i at exactly the same rotational rate as the gear 68 turned by the flexible shaft 36, since the tooth ratio of gears 88 and 1G is the same as that of the gears I85 and I86. It further follows, with reference to the differential assembly 22, that lagging of the engine turned gear 38-I86 with respect to the oppositely turning master speed" gear 28 will produce advancing thread rotation of the threaded spindle 3i (with corresponding left-hand movement of the slidable base 48, spring 41 and flared out spindle portion 49, resulting in closing of contact points 56a51) while over-speeding of the engine turned gear 38-I86 will produce retracting thread rotation (and closing of contact points 56b-58).

To make possible the synchronous operation of the propeller blades 63a and 63b shown in Fig. 4, a wire conduit I81, fixed to a crankcase I 88 of the engine 88a by means of a clip I89 and cap screw H8, is provided for housing the wiring scheme of Fig. 1. That much of the aforesaid wiring as pertains to electrical connections between the propeller pitch changing motor 58a, the switch panel I, and the motor-generator set (3-4) is led through a conduit branch III to the rear face of the propeller 64. The remainder of the aforesaid wiring is led through a conduit branch H2 to the synchronizer unit "a. As has been previously stated, the synchronizer unit 11a is directly connected to the engine 60a by means of the flexible shaft 36 provided with the retain ing collar 31 and the square tipped driving end 38.

To operate the all-electrical embodiment of my invention, the aircraft pilot advances all engine throttles to a desired setting and closes the double pole switches 6 and 1 of the panel I. He thereafter adjusts the rheostat control 8 such that the tachometer 2 indicates a desired engine speed, as for instance 2000 revolutions per minute. Since the motor-generator set (3-4) of Fig. 1 turns as a single unit, the alternating current motors 20a and 20b of the synchronizer units Na and Ill) will turn at exactly the same number of revolutions per minute. The pilot then closes the single pole switches I03 and I04 of Fig. l, causing equal and like directional rotation of the gears 40 and 30-406 of the synchronizer units Ila and Hi). It is at once evident that the previously stated inability of an aircraft pilot to successfully synchronize several engines of a multi-engined power plant by mere tachometer corrected throttle readjustment is no longer involved. Each of the alternating current motors 20 is turning at exactly the same number of revolutions per minute. The fact that the aforesaid like revolutions are jointly slightly greater than or slightly less than the revolutions indicated on the dial of the tachometer 2 is of no significance. What is essential to note is that a difference of but one revolution per minute between engines 90a and 60b and a predetermined master speed setting of the alternating current motors 20a and 20?) will cause one complete revolution per minute of the threaded spindle 3i shown in Fig. 2. Thus, through application of differential actuated contactors to the spring portions of the governors heretofore utlized to control electrically operated variable pitch propellers, I provide a degree of synchronism never before attained.

In Figs. 3 and 5, I disclose the combined electric-hydraulic synchronizer system previously referred to in the initial description of Fig. 1. The revised synchronizer unit I8a contains a new housing portion II3 incorporating a fluid control valve II4 for operating a variable pitch propeller having centrifugal weights to turn the propeller blades to their high pitch position. A brief description of Fig. 5 will make more readily understandable actuation of the valve II4 by a revised counter weighing mechanism I I5.

A propeller H6 is mounted upon the forward end of an aircraft engine II1. It consists of a hub II8 to which are rotatably mounted blade sockets IISa and Hill) for carrying propeller blades I20a and I20b; of centrifugal counterweights I2Ia and I2Ib for automatically maintaining the aforesaid propeller blades in a high pitch position; and of a propeller pitch changing fluid motor I22, an extendable housing portion of which is shown partially retracted within the hub [I8. Application of oil pressure within the fluid motor I22 causes the extendable housing portion thereof to assume a series of forwardly progressing positions terminating in the maximum dotted position shown in Fig. 5, at which position the propeller blades I20a and I20b will assume a maximum low pitch position. The synchronizer unit I8a is mounted upon the lower forward portion of a crankcase I23 of the engine II1 by means of cap screws I24 and lock washers I25. The motor 20 of the housing portion I9 is provided with a wire conduit I29 flxed to the crankcase I23 by means of a clip I21, cap screw I28 and lock washer I29. An oil Inlet I30, provided upon the exterior surface of the housing portion H3, is directly connected with the oil pump providing general lubrication for the engine II1 by means of an exterior oil line I3I and such additional lines within the crankcase I23 as may be required. An oil inlet-outlet I32 is operably connected with the propeller pitch changing fluid motor I22 by means of an exterior oil line I33 and further internal pipings and slip rings contained within the crank case I23 and the hub I I8. Lastly, an oil outlet I34 is operably connected with the oil sump of the engine II1 by means of an exterior oil line I35 and such further internal piping as may be required. Briefly restated, to obtain maximum low pitch position of the propeller blades I20a and I20b, oil must flow from pump to inlet I30 and from thence through inlet-outlet I32 to the motor I22. On the other hand, if decrease in engine revolutions is desired, oil must drain from the motor I22 into inlet-outlet I32, and from thence return to the engine sump through the outlet I34. 'I'heaforesaid oil drainage is accelerated by the centrifugal action of the counter-weights I2Ia and I2Ib which automatically decrease unwanted increases in the speed of the engine II1 through increase in propeller blade pitch angle.

The detailed construction of the fluid control valve I I4 and revised counter-weighing mechanism H5 is shown in Fig. 3. A piston chamber I36 is provided with a header I31 (flxed by means of screws I38 and lock washers I39), a fluid bypass I40 and fluid ports I4I, I42, and I43. The port I4I leads directly into the oil inlet I30, the port I42 similarly into the oil inlet-outlet I 32, and the port I43 into the outlet I34 of the new housing portion H3. As long as the combined weight and L-shaped supporting arms 43 retain the neutral positioning of Figs. 2 and 3, like neutral positioning of the piston and rod assembly I44 obtains; i. e., a head I45 of the assembly I44 is centrally disposed with reference to closing of the port I42, while a head I46 of the assembly I44 is sufficiently positioned to the right of the port I4I to avoid any possibility of overlapping the same. It should also be noted that extreme right-hand actuation of the piston and rod assembly I44 positively closes off the port MI.

The right-hand extremity of new spindle I41 is provided with a flattened end I48 adapted to receive the upper end of a yoked lever I49. The lever I49 depends from a mounting pin I50 fixed to a yoked boss I5I forming a part of new insulating sheet I52. A driving pin I53, fixed to the end I48 of spindle I41, slides longitudinally in an elongated slot I54 of the lever I49 such that right-hand movement of the spindle I41 will cause counter-clockwise movement of the lever I49 in response to over-running of the flexible shaft 36 with respect to the alternating current motor 20. On the other hand, under running of the flexible shaft 36 with respect to the alternating current motor 20 causes clockwise movement of the lever I49 such that an elongated slot I55 provided in the lower extremity thereof will cause a driven pin I56, fixed to the left extremity of the piston and rod assembly I44, to move to the left.

Right-hand movement of the piston and rod assembly I44 has the following effect. The head I45 uncovers the port I42 (connected to fluid motor I22) allowing oil therefrom to escape to th engine sump through the port I43. Regardless of the particular degree of engine throttle setting, the aforesaid escapage of oil is attended with immediate increase in the pitch angle of the propeller blades IZOa and I2IIb. On the other hand, left-hand movement of the piston and rod assembly I causes the head I45 to uncover the port I42 to intercommunication with the port I, whereupon oilunder pressure will immediately flow to the fluid motor I22 (causing decrease of propeller blade pitch). In both of the aforesaid movements, that portion of the piston chamber I36 lying to the immediate right of the head I46 is freely vented to the engine oil sump by means of the bypass I40.

Fig. 3 also shows the detailed construction of the combination spider-clutch 26 driving the threaded spindle 3|. A spider I51 is provided with gear Journals I58, washers I 59, and cotter pins I60 for retaining the differential gears 21; with a clutching surface NH; and with a clutch surface centralizing bearing I62. The mating portion for the spider I51 consists of a clutch plate 863, a backing plate I64 fixed to the threaded spindle 3| by means of a pin I65 and four plate separating springs I65. that maximum expansion of the counter Weighing mechanism M is limited by seating of the right extremity of the sliding base 48 upon the left extremity of a bushing I61 utilized as a support for the central portion of the threaded spindle- SI. On the other hand, maximum contraction of the counter weighing mechanism. 44 will occur upon closing of the loops of the com- It will b noted operative in response to a difference in the speeds pression spring A l. It is therefore essential that I the spindle 3| entirely cease rotation when either of the aforesaid limiting positions of the counter weighing mechanism 44 has been reached. This is accomplished by slippage between the clutch surface MI and the clutch plate I63 of the combination spider-clutch 26.

Although the description is specific to the illustrations in the drawings, it is to be understood that there may be numerous departures therefrom which will still be within the field and scope of my invention, so that I do not wish to be restrict-ed thereto, but only in so far as the appended claims are solimited.

I claim:

1. In a mechanism for synchronizing the speed of a controlled engine with the speed of a reference speed means, a centrlfugally actuated governor driven by said controlled engin and having variable loading means, a difierentia mechanism disposed between said engine and reference speed means and having its opposite sides driven, respectively, by said controlled engine and said reference speed means, a displaceable member operatively connected with said variable loading means and associated with said differential mechanism to be displaced by the latter upon a variation in the speed of said engine with respect to said reference speed means, means for drivingly connecting and disconnecting said controlled enor said rotating member and said reference speed driven member for varying the regulation of said governor, means for rendering said last mentioned means inoperative including means, operative at will, for effecting a disengagement or engagement of said rotatable members through said speed difference responsive means, and means operative upon a predetermined change in the condition of said rotatable members to drivingly disengage the same through said speed diflerence' responsive means.

3. In a mechanism for synchronizing the speed of a controlled engine with the speed of a constant speed means, a centriiugally actuated governor driven by said controlled engine and having variable spring loading means, a differential mechanism disposed between said engine and constant speed means and having its opposite sides driven, respectively, by said controlled engine and said constant speed means, a spindle having one end operatively connected with said variable spring loading means and the other end fixed to the spider portion of said differential mechanism to be displaced by the latter upon a variation in the speed or said engine with respect to said constant speed means, and means disposed between said engine and the engine driven side or said diiferential for connecting or disconnecting the same.

4. In a mechanism for synchronizing the speed of a controlled engine with the speed of a constant speed means, a centrifugally actuated governor driven by said controlled engine and having variable spring loading means, a differential mechanism disposed between said engine and constant speed means and having its opposite sides driven, respectively, by said controlled engine and said constant speed means, a spindle having one end operatively connected with said variable spring loading means and the other end fixed to the spider portion of said differential mechanism to be displaced by the latter upon a variation in the speed of said engine with respect to said constant speed means, and means disposed between said engine and the engine driven side of said differential for rendering the latter inoperative.

5. In a mechanism for synchronizing the speed of a controlled engine with the speed, of a constant speed means, speed control means for varying the speed of the controlled engine, a centrifugal governor driven by said engine, connecting means between said governor and said engine speed control means for actuation of said control means to increase or decrease the speed of said engine on its departure from the speed setting of said governor, a three legged difierentiai mechanism disposed between said engine and. said constant speed means and having a first leg driven by said con-= trolled engine, a second leg driven by said constant speed means, and third leg operatively connected with said governor to serve as a modifier or the speed setting thereof and associated with said first and second legs to be displaced thereby upon a variation in the speed of said engine with respect to said, constant speed means.

6., In a mechanism for synchronizing the speed of a controlled engine with the speed of a reference speed means, speed control means for varying the speed of the controlled engine, a centrifugal governor driven by said engine, connecting means between said governor and said engine speed control means for actuation of said control means to increase or decrease the speed of said engine on its departure from the speed setting of said governor, a three-legged differential mechanism disposed between said engine and reference speed means and having a first leg driven by said controlled engine, a second leg driven by said reference speed means, a third leg operatively connected with said governor to serve as a modifier of the speed setting thereof and associated with said first and second less to be displaced thereby upon a variation in the speed of said engine with respect to said reference speed means, and meansfor eflecting an engagement or disengagement of the said controlled engine and said reference speed means through said difierential at will.

7. In a mechanism for synchronizing the speed of a controlled engine with the speed of a reference speed means, speed control means for vary- ,ing the speed oi the controlled engine, a centrifugal governor driven by said engine, connecting means between said engine speed control means for actuation of said control means to increase or decrease the speed of said engine on its departure from the speed setting of said governor, a three-iegged difierential mechanism disposed between said engine and reference speed means and having a first leg driven by said controlled engine, a second leg driven by said reference speed means, a third leg operatively connected with said governor to serve as a modifier for the speed setting thereof and associated with said first and second legs to be displaced thereby upon a variation in the speed of said engine with respect to said reference speed means, and electromagnetic means for effecting an engagement or disengagement of the said controlled engine and said reference speed means through said differential.

8. A synchronizing system for prime movers comprising in combination an engine, speed control means for varying the speed of the engine, a constant speed motor including means for adlusting the speed thereof to a selected value, a speed responsive centrifugal governor driven by said engine, connecting means between said governor and said engine speed control means for actuation of said control means to increase or means decrease the speed of said engine on its departure from the speed setting of said governor, a modifier for said governor operative to vary the speed setting thereof, said governor being operative to vary the speed of said engine upon any variation in the engine speed from the speed determined by the instant speed setting of said modifier, a three-element differential having one element rotatably connected to be driven by said engine in accordance with the speed thereof, a second element rotatably connexzted to said constant speed motor to rotate in accordance with the speed thereof and a third element interconnected to said first and second elements and operatively connected to said governor modifier to vary the speed setting of said governor in accordance with the difference in speeds of said engine and said constant speed means.

9. The combination with an engine, a propeller for absorbing the power of said engine and means for changing the pitch of said propeller to thereby vary the speed of the engine, of motor means driven at a constant speed, a centrifugal governor driven by said engine and including a modifier, connecting means between said governor and said means for changing the pitch of the propeller for actuation of the pitch-changing means to increase or decrease the speed of said engine on its departure from the speed setting of said governor, a three-legged differential mechanism disposed between said engine and said constant speed motor means and having a first leg driven by said engine, a second leg driven by said constant speed motor means, and a third leg operatively connected to said governor modifier and to said first and second legs of differential mechanism to act upon said pitchchanging means in accordance with the speed difference between the speed of the engine and the speed of said constant speed motor means.

10. The structure as claimed in claim 9, including manually controlled means operable at will for rendering said difi'erential inoperative to act on said governor modifier.

DANIEL A. DICKEY. 

